Amplitude detection circuits are used to compare an input electrical signal against a reference signal, typically a voltage. The circuit generates an output, usually a high voltage (digital one), for an input signal amplitude greater than the reference signal and generates a different output, usually a low voltage (digital zero), for an input signal amplitude less than the reference signal.
The Figures illustrate specific aspects of the circuits. Together with the following description, the Figures demonstrate and explain the principles and operation of the circuits. In the drawings, the schematic circuit elements can represent their equivalent structures and connections. The same reference numerals in different drawings represent the same element, and thus their descriptions will not be repeated.